Developing carborane-based functional polymeric architectures
The research presented in this thesis focuses on the development of novel functional hybrid organic-inorganic architectures containing chemically-tethered icosohedral carboranes. The motivation behind this work was to understand and overcome the challenges associated with the incorporation of inorganic boron clusters into a variety of well-defined polymeric architectures. This task was critical for the advancement of scientific understanding, as well as the improvement and implementation of novel hybrid materials towards technological applications. Chapter 1 illustrates some of these potential target applications, and highlights the advantages associated with the utilization of hybrid materials, in particular those containing boron.
The synthesis of a novel silyl-protected oxanorbornene imide carborane (SONIC) monomer as well as its copolymerization by ring-opening metathesis polymerization (ROMP) to obtain amphiphilic diblock copolymers is described in Chapter 2. The subsequent functionalization and labeling of the polymers, and their solution behavior have been investigated. Initial biological studies have shown the incorporation of the carborane-containing polymers in carcinoma cells. These findings pave the way for future investigations of these polymeric architectures as delivery agents for boron neutron capture therapy in cancer treatment.
The random copolymerization of SONIC and cyclooctene is reported in Chapter 3. Polymers with varying compositions have been obtained and hydrogenated to afford polyethylene-like materials. The structural and thermal properties of these materials have been evaluated and compared to model compounds.
Carboranes have also been introduced into conjugated polyaromatic structures as side chains. The synthesis of a polyfluorene monomer having two pendant silylcarborane groups is reported in Chapter 4. The homopolymerization of this monomer, and its copolymerization with 2,7-dibromo-9,9-di-n-hexylfluorene by microwave-assisted nickel(0)-mediated coupling was investigated. The advantage offered by the presence of bulky silylcarborane groups is described.
Finally, the versatility of carborane-containing polymers is demonstrated through their utilization as resists for nanoimprint lithography (NIL). A novel silylcarborane-containing acrylate has been synthesized as described in Chapter 5. The utilization of only 10 wt% of the carborane-containing resist lead to a two-fold decrease in etch rate. Excellent image transfer was also observed, allowing for the fabrication of gold interdigitated electrodes. This work provides a new set of tools for the efficacious implementation of NIL.